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arXiv · 1602.00656

Aspects of electron-phonon interactions with strong forward scattering in FeSe Thin Films on SrTiO$_3$ substrates

Y. Wang·K. Nakatsukasa·L. Rademaker·T. Berlijn·S. Johnston
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Abstract

Mono- and multilayer FeSe thin films grown on SrTiO$_\mathrm{3}$ and BiTiO$_\mathrm{3}$ substrates exhibit a greatly enhanced superconductivity over that found in bulk FeSe. A number of proposals have been advanced for the mechanism of this enhancement. One possibility is the introduction of a cross-interface electron-phonon ($e$-$ph$) interaction between the FeSe electrons and oxygen phonons in the substrates that is peaked in the forward scattering (small ${\bf q}$) direction due to the two-dimensional nature of the interface system. Motivated by this, we explore the consequences of such an interaction on the superconducting state and electronic structure of a two-dimensional system using Migdal-Eliashberg theory. This interaction produces not only deviations from the expectations of conventional phonon-mediated pairing but also replica structures in the spectral function and density of states, as probed by angle-resolved photoemission spectroscopy, scanning tunneling microscopy/spectroscopy, and quasi-particle interference imaging. We also discuss the applicability of Migdal-Eliashberg theory for a situation where the \ep interaction is peaked at small momentum transfer and in the FeSe/STO system.

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Y. Wang, K. Nakatsukasa, L. Rademaker, T. Berlijn, S. Johnston. 2016-02-01. Aspects of electron-phonon interactions with strong forward scattering in FeSe Thin Films on SrTiO$_3$ substrates. https://doi.org/10.1088/0953-2048%2F29%2F5%2F054009

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